Brush cleaning device



June 26, 1956 M. 1. TURNER, JR, ETAL 2,751,616

BRUSH CLEANING DEVICE Filed July 17, 1955 FIGS INVENTOR. MILO l. TURNER JR. CLYDE R. MAYO g gAfih ML ATTORNEY 2,751,616 Patented June 26, 1956 BRUSH CLEANING DEVICE Milo I. Turner, Jr., Livonia, and Clyde R. Mayo, Rochester, N. Y., assignors to The Haloid Company, Rochester, N. Y., a corporation of New York Application July 17, 1953, Serial No. 363,692

2 Claims. (CI. 15-77) This invention relates in general to xerography and, in particular to apparatus for the removal of electrostatically adhering particles from an insulating surface.

In the art of xerography it is usual to form an electrostatic latent image and to develop this image with an electrostatic attractable material which generally is a thermoplastic resin powder. This developed image is then transferred to a second surface. The transfer step causes a large amount of the resin material to adhere to the new base material but a significant proportion may remain on the original image bearing base.

An object of the present invention is the removal of this residual material from the xerographic plate and the problem is complicated by the fact that developer is electrostatically attracted to the xerographic plate surface and by the further problem that both the xerographic plate surface and the developer powder are, relatively speaking, electric insulators.

A problem exists with apparatus presently in use in that the residual material is not sufliciently removed for high quality reproductions and for rapid processes. Further each incomplete cleaning operation may leave a thin film on the plate. This eflect is progressive. The more film there is, the faster additional films build up. For automatic machines this is a serious limiting factor since frequent solvent cleaning is almost out of the question in that it means stopping the machine for servicing. Also, this film may be a significant factor in plate life.

It is therefore another object of this invention to produce a novel apparatus for the rapid and thorough removal of the residual particles from the surface of a xerographic plate through the use of a rapidly rotating vacuum creating brush.

Additional objects of the invention will in part become obvious and will in part become apparent from the specification and drawings wherein:

Figure 1 is a diagrammatic cross sectional view of one embodiment of the invention wherein a flat insulating surface is cleaned;

Figure 2 is a diagrammatic cross sectional view of another embodiment of the invention wherein a cylindrical insulating surface shown in section is cleaned;

Figure 3 is a diagrammatic cross sectional view of another embodiment of the invention in an apparatus designed to remove residual material from a xerographic plate in a xerographic plate holder.

Referring more particularly to the drawing and to the embodiments of the invention therein shown for purposes of illustration, in Figure l, generally designates the surface of a xerographic plate. The plate is generally constructed so that a conductive layer 11 underlies a photoconductive insulating layer 10. A cylinder 12 is provided with a brush 14. The length of the cylinder 12 is dependent upon the width of the xerographic plate 15. A flicking member 16 extends from the hood generally designated as 18 into the area of rotation of the brush 14. An area of the hood 18 is made up of a filter 20. The entire apparatus shown in Figure 1 is enclosed by the hood 18 except between the points 16 or the flicking member and the top edge of the hood. Between these points, the brush 14 is disposed and positioned to ride above the enclosed area of the hood and thereby contacts the photoconductve insulating surface 10 of the xerographic plate 15.

In Figure 2 a cylinder is shown in section with a surface 29 made up of a photoconductive insulating material and used as the face of a xerographich plate; a cylinder 26 with an outer brush layer 27 which, when rotating, contacts with the brush layer 27, the surface 29 of the cylinder 25; a rod 28 positioned in such a way as to be within the area of rotation of the brush 27 and thereby causing the brush 27 to be compressed as it passes the rod 28.

In Figure 3 another embodiment of this invention is shown in which an outside covering generally designated as have as an integral part thereof a filter 52. Leading into the device through wall 35 is an opening or slot 57 positioned and adapted to admit a xerographic plate 49, in a plate holder 47 to guide ways provided along the sides of slot 57. The head 46 of a microswitch 45 rides up into this opening 57 when the plate 49 is not in the apparatus. When the plate 49 is placed in the slot 57 the head 46 is depressed into the position shown, closing a circuit causing the motor generally designated as 38 to rotate, causing the belt generally designated as 39 to turn the cylinder generally designated as 40. Cylinder 40 has an outer brush layer 41 which comes in contact with the surface of the xerographic plate 59 and the flicking edge 42. At the end of the opening 57 is provided a spring 44. This spring 44 is depressed when the xerographic plate 49 is inserted into slot 57. When the pressure used to insert the xerographic plate 49 is released, the spring 44 will cause the xerographic plate 49 to be displaced partially out of the slot 57 to a point where it can be grasped and removed. A protective apron 51 is provided between the opening or passageway generally designated as 53 and the opening generally designated as 57 and extends from the flicking edge 42, along the face of the xerographic plate surface 59 and up to the filter 52.

in use and operation cylinder 12 of the embodiment shown in Figure 1 is energized from an external source. if the apparatus shown in Figure l is part of a manually operated xerographic apparatus, the cylinder can optionally be energized by throwing a switch to cause a motor to rotate and drive the cylinder. If the apparatus shown in Figure 1 is part of an automatic xerographic apparatus, the cylinder can be caused to rotate when the automatic apparatus is put into operation. When the apparatus is being used as an element in an automatic xerographic device, the cylinder 12 may optionally be constructed so that the brush may be removed from contact with the plate. The flicking member 16 is constructed so that it runs the length of the cylinder 12 and is positioned to compress an entire brush section as a brush section passes the flicking member. After a section of the brush has been compressed by the flicking member it passes into a vacant zone and then is brought into contact with the xerographic plate surface. It is not intended to limit this invention to any specific theory or mechanism of operation, however, one explanation of a possible theory follows. Any powder on the plate surface is removed by a number of co -operating elements as the sensitized plate surface is brought into contact with the brush. The individual bristles of the brush which were compressed as they passed the rod, flicking member, or flicking edge tend to spring up of their own accord due to the effects of centrifugal force in the vacant zone. In tending to ex.- tend outward due to centrifugal force after being compressed, the bristles contact the plate with more than normal wiping force. When a section of the brush is compressed by the flicking member all air in that section is driven from the brush. When this section of the brush reaches the vacant Zone there is a rush of air to the brush area to equalize pressure. Additional air is brought to this area by the movement of the bristles seeking their normal position. The flicking member has, by compressing the bristles, driven the normal air supply from between the bristles, and air will be drawn into that area of the brush to fill the vacuum after the brush area passes the flicking member. A wind is also established following the direction of rotation of the cylinder. This combined air current travels across the surface of the plate while the brush is brought in contact with the plate. The air current and air filled brush section are brought under pressure when the brush section is brought into contact with the plate surface and the brush, having made friction contact with the flicking member, the plate surface, and the particles on the plate, draws those particles on the surface of the plate which are not blown or wiped into the hood. These factors combined produce a thoroughly cleaned plate rapidly. The particles which have been blown or wiped into the hood are carried by the air current within the hood. Any particles adhering to the brush are dislodged when the brush contacts the flicking member due to the sudden deceleration of the bristles or due to the compressing and wiping 'by the flicking member or due to physical removal by the outrush of or due to an electrostatic reaction that takes place when the brush contacts the flicking member or due to a combination of these elements. These particles are likewise thrown into the air currents within the hood. The air currents within the hood are in the direction of rotation of the brush except at the region where the brush makes contact with the flicking member. At this point air is compressed out of the brush and two opposing currents meet and tend toward the area'of least resistance or pressure, or the area where the filter 2% is placed, the filter allowing the air currents to escape from within the hood area.

The edge of the hood is constructed so as to be as close as possible to the surface of the plate without making contact with the delicate surface. articles removed from the plate surface are not thrown through the slight space that exists between'the edge of the hood and the plate surface due to a negative pressure that exists in the brush surface as the brush surface passes from. the points of last contact with the plate. This lower pressure area causes air to be sucked in from without the hood through this opening and adds to the wind currents in the hood thereby preventing any of the removed particles from being thrown through this opening.

The fact'that a negative pressure exists at the area where the brush surface passes from the point of last contact with the plate creates at this point a vacuum effect which also cooperates with the other factors in removing electroscopic material from the plate surface.

In Figure 2 another embodiment using a rotating cylinder 25 shown in section is illustrated. The brush 27 is mounted on a cylinder 26 which can optionally be placed so that it remains in contact with the rotating cylinder 25 at all times or so that it may be removed from contact with the rotating cylinder 25 during cycles. The photo sensitive xerographic plate surface 2% is cleaned in a similar manner as the Xerographic photosensitive plate surface i in Figure l was cleaned. When the cylinder 26 is positioned to clean the Xerographic photosensitive surface 29 the brush 27 w ll contact both the rod 28 and the kerographic plate surface 29. The explanation of the nethod for cleaning the device found in Figure 1 will also apply to the device found in Figure 2. Optionally, a hood similar to the hood provided in Figure 1 can be provided-forthe apparatus in Figure 2 or some other device to collect the particles removed from the xerographic plate surface 29 and so that air currents as discussed above will be created. I

The illustrative device shown in Figure 3 is specifically constructed to clean a xerographic plate 45 in a Xerographic plate holder 47. As the Xerographic plate is inserted in slot 57 a circuit is closed through micro-switch 45 causing the cylinder 40 with the brush surface 41 as an outer layer to rotate. The cylinder 49 with the brush surface 41 as an outer layer will continue to rotate at all times while the xerographic plate is in opening 57. Since the cylinder 40 is in a relatively fixed position the brush surface 41 will always, while rotating contact the flicking edge 42. The direction of wind currents in this embodiment generally follow the direction of rotation of the cylinder 40 as the wind currents in Figure l and Figure 2 generally followed the direction of rotation of the cylinders 12 and 26. The particles removed from the surface 59 of the xerographic plate 49 are therefore thrown into ti e opening 53 and directed toward the filter 52. The apron 51 acts as a shield between the opening 53 and the xerographic plate member in the opening 57. It thereby prevents any of the removed particles from falling back on the plate surface. The Xplanation given for the device shown in Figure l as to how the plate surface is cleaned would apply to the device shown in Figure 3.

It has been found that the direction of rotation of the brush is not critical as long as the rod, flicking member or flicking edge is positioned to contact the brush at a point along its direction of rotation just before the brush contacts the plate surface and therefore applicants invention is not limited to any specific direction of rotation, however, it is preferred to rotate the brush in a direction so that the bristles pass over the plate surface in a direction opposite to the direction of the movement of the plate, in that a dirty brush surface will not contact a cleaned plate surface. When working with powder materials conventionally used in the xerographic process, it has been found that a relatively high brush speed is necessary in order to produce thorough cleaning rapidly. The brush speed is variable within limits, depending on the nature of the powder material being removed, the brush material being used, the contact being made by the brush against the plate surface and the speed with which the plate surface passes over the brush, and other related factors. With present commercial Xerographic developers it has been found that a minimum speed of 20 feet per second is required and a highly efficient speed is achieved with a brush rotation of 1800 revolutions per minute using a brush layer on a cylinder of 3 to 5 inches in diameter.

It has been found that the brush material should have certain desirable characteristics for proper operations. The material should be sufficiently soft so that it does not abrade the delicate insulating surface, and at the same time it should be sufliciently stiff so that the brush itself does not become matted upon repeated use. Another desirable characteristic is that the material should be such that it does not deposit any oil or liquid on the surface being cleaned, or that any material thus deposited be non-injurious'to the xerographic plate surface and the xcrographic system. Other properties of the brush which lead to improved efficiency of operation appear to be proper position in the triboelectric series and proper humidity characteristics. In addition, it is desirable that the brush itself be relatively wear resistant to obviate frequent replacement.

Fiber materials, furs and the like may be used including, for example, synthetic fiber materials such as nylon, cellulose derivatives and the like, and natural fibers such as cotton, wool, hair and the like. Among the materials which have been satisfactorily used with a cleaning brush are various types of furs, such as, for example, beaver fur, grey fox fur, New Zealand sheared and dyed rabbit fur, and the like.

The usual procedure in preparing a material for use as a cleaning brush is to give the raw fur or other material a thorough washing preferably with usual dry cleaning solvents in order to remove greases and the like. On the other hand, it frequently is desirable to treat the brush material to control the conductivity of the brush, either to make the brush conductive or to make it nonconductive, as desired. Thus, for example, a fur may be treated with a small quantity of an electrically conductive impregnating material to improve its conductivity and thus assist in the neutralization of residual electric charge on the powder particles.

A variable factor referred to above as influential in the cleaning process is the contact made by the brush with the xerographic plate surface. Since the contact made by the brush surface with the plate surface can effect efliciency, it is preferred that the cylinder having an outer layer of fur be constructed and mounted so that it is adjustable from a point where the edge of the bristles just touch the surface of the plate to a point where almost the entire bristle contacts the surface of the plate. It has been found desirable to bring from one-thirty-second to one-fifth of the bristle length into contact with the plate surface when the cylinder with the outer layer of brush is rotating at approximately 1800 cycles per minute for excellent cleaning.

It is also desirable to construct and mount the rod, flicking member, or flicking edge adjustably so that the contact made by the rod, flicking member, or flicking edge with the brush layer is variable and controllable. Using a cylinder of from 3 to 5 inches in diameter rotating at 1800 revolutions per minute it has been found desirable to adjust the rod, flicking member, or flicking edge to contact the brush surface by extending /z of the distance between the outer edge of the extended brush material and the cylinder.

The rod, flicking member, or flicking edge may or may not be a conductor and it may or may not be grounded; however, it has been found that a grounded conductive material produces more efiicient operation in the present state of the art. The edge of the rod which contacts the brush should be constructed in such a way as to inhibit Wear of the brush material.

Optionally the hood itself may, if desired be constructed and adapted to operate both as the hood and rod, flicking member, or flicking edge by bringing an area of the hood into contact with the brush layer.

The hood should be constructed in such a way as to allow sufficient clearance between the hood and brush surface so that the air currents can function properly. It has been found that a clearance of /e between the outer edge of the brush material when extended and the hood is proper for eflicient operation.

The filter is constructed and placed in the apparatus in such a way as to be easily removed and replaced. The filter may be any material which will catch the particles removed and yet allow free passage of air. An example of a type of filter used would be a standard glass wool filter often found in home heating systems.

What is claimed is:

1. Apparatus for removal of electrostatically adhering particles from a xerographic plate surface comprising a rotatable brush mounted within a hood, means to support a xcrographic plate surface to be cleaned in contact with said brush, means to guide the surface to be cleaned past the rotatable brush, means for rapidly rotating the brush, flicking means along the length of the brush to compress the brush whereby air from between the brush bristles is expelled, said flicking means for compressing the brush comprising a member positioned at a point along the direction of rotation of the brush just before the brush contacts the plate surface and positioned to impinge substantially deeper into the brush bristles than does the surface to be cleaned, a passageway disposed to receive air ejected from the brush and convey said air away from the hood area, said passageway extending to said flicking means and the hood thereby maintaining removed particles away from the surface being cleaned.

2. Apparatus for the removal of elcctrostatically adhering particles from a xerographic plate surface in a xerographic plate holder comprising a cabinet with a filter mounted thereon, and opening to receive a xerographic plate in a xerographic plate holder, a switch mounted within the opening and operable by insertion of a xerographic plate in a xerographic plate holder therein to energize a motor to cause a brush to rotate when a xerographic plate in a xerographic plate holder is in serted in the opening, a spring mounted at the far end of the opening to cause a xerographic plate in a xerographic plate holder to be displaced out of the opening, an apron positioned and disposed within the cabinet above and across the opening, a flicking edge mounted on the apron and positioned and disposed to contact and depress the brush along its length at a point along its direction of rotation just before the brush contacts the plate surface as it rotates past the flicking edge attached to the apron, the flicking edge and apron as a unit acting to prevent any removed particles from returning to the xerographic plate surface, the brush being positioned and disposed to contact the xerographic plate surface across the width of the xerographic plate in the xerographic plate holder, as the xerographic plate in the xerographic plate holder is inserted and removed into and out of the opening.

References Cited in the file of this patent UNITED STATES PATENTS 295,470 Zeigler Mar. 18, 1884 1,081,375 Evert Dec. 16, 1913 1,567,693 Allen et al Dec. 29, 1925 1,759,881 Bentley May 27, 1930 1,774,326 Holmes Aug. 26, 1930 2,145,495 Paxton Jan. 31, 1939 2,357,809 Carlson Sept. 12, 1944 FOREIGN PATENTS 60,472 Switzerland of 1912 

